Just when you thought fancy effects on Linux desktops started to get remotely understandable, focussing on Aiglx/Xgl with Compiz, a fork of Compiz is announced: Beryl. This is the logical continuation of the popular compiz-quinnstorm branch, used by many Ubuntu users. "During this summer, and during the last few weeks, some major additions were done in compiz-quinnstorm, bringing a whole new decorator, cgwd, which was designed to be fully themable, and a new settings backend, csm, which intended to drop most of the gnome deps - there were other reasons for this, but this is not our current subject. Consequently, we reached a situation where it's quite impossible to come back." The main reason is general unwillingness to work with and unresponsiveness to the developers of the -quinnstorm branch from the official Compiz guys.

The quinnstorm branch started as a patch to the official compiz to include some experimental plugins made by the comunity but in the later times it has become a window manager for itself.
As compiz developers didn't realize that themeable windows was a good point in modern desktops, the quinnstorm branch developed GCWD (Gnome Configurable Window Decorator). Later, just because the complains about using gconf to configure compiz (as it declares to be desktop-agnostic) it changed it's configuration system to CSM (Compiz Settings Manager) so since then all the tools made for the official compiz were incompatible with the quinnstorm compiz. I personally think that the fork was actually the first version using csm, now comes the official confirmation.

Anyway, for me it doesn't matter because in the end, Metacity and KWin will implement their own effects and we are going to use the official window manager of the Desktom Manager of choice.

As compiz developers didn't realize that themeable windows was a good point in modern desktops

That does not seem like a fair evaluation to me. To quote from the TODO file of the gnome-window-decorator:

* Plugin interface

* Plugin with SVG-based theme support

* Plugin that supports old metacity themes

cgwd made a very rushed and somewhat buggy impression on me. While it is good to have, I would not consider it a complete superset of gnome-window-decorator just yet. In any case, this is hardly a problem since window decorators are replacable already.